1. Field of the Invention
The present invention relates to a torque clutch apparatus and printer apparatus which are suitable when being applied to a color roll printer, for example.
2. Description of the Related Art
In a printer apparatus using ink ribbon, when ink ribbon slackens during printing, it may wrinkles so as to deteriorate printed images.
Therefore, in such a conventional printer apparatus, by controlling a winding reel and/or feed reel of ink ribbon with torque clutches such as felt clutches, a constant tension is applied to the ink ribbon.
However, according to such a method, since the diameter of the roll of ink ribbon wound on the feed reel and the diameter of the roll of ink ribbon wound on the winding reel gradually change due to printing, there is a problem that a constant tension cannot be always applied to the ink ribbon.
As for techniques for solving such a problem, there may be a first method of controlling the output of a motor and a second method of using a torque clutch with a variable output-torque such as a powder clutch and a hysteresis clutch. According to the first method, there has been a problem that the travelling stability of ink ribbon is damaged due to non-uniform feed motion of a gear or belt. According to the second method, there have also been problems that cost is increased and the entire printer apparatus becomes large in size and weight, because the powder clutch and hysteresis clutch are very expensive and large in size and weight.
In view of the problems described above, the present invention has been made and it is an object of the present invention to propose a simple and lightweight torque clutch apparatus capable of freely changing a torque, and a printer apparatus capable of stably controlling tension of ink ribbon by a simple structure.
In order to solve these problems, according to the present invention, a torque clutch apparatus comprises a shaft which is rotatably pivotably mounted and which has a screw thread formed on the circumferential surface thereof, a first gear rotatably fitted to the shaft, first and second sandwiching members fitted to the shaft so as to sandwich the first gear therebetween and to rotate integrally with the shaft, a second gear rotatably screwed on the shaft, and a spring arranged between the second gear and one of the first and second sandwiching members opposing the second gear. Therefore, the torque clutch apparatus is simple in construction and the output torque can be freely changed by rotating the second gear.
Also, according to the present invention, a printer apparatus comprises first torque-generating means for generating a variable load torque applied to a feed reel, which is rotatably supported, of ink ribbon; second torque-generating means for variably generating a rotational torque to a winding reel, which is rotatably supported, of ink ribbon; and controlling means for controlling the first and/or second torque-generating means so as to generate one of the load torque and rotational torque in accordance with the diameter of the roll of ink ribbon wound on the feed reel and/or the winding reel. As a result, the printer apparatus can maintain the tension of ink ribbon constant at all times.